1. Field of the Invention
The present invention relates to an electrical connector, and particularly to a Zero Insertion Force (ZIF) electrical connector for electrically assembling a chip module to a printed circuit board.
2. Description of the Related Art
The related detailed description about a ZIF electrical connector and its operation of the relevant ye is disclosed in U.S. patent application filed by Wei-Yao Lin and entitled xe2x80x9cZero Inserted Force Connector Socket With Helical Driving Mechanismxe2x80x9d which was filed on Feb. 9, 2000 and has a Ser. No. 09/501,333, now U.S. Pat. No. 6,280,223.
In the above pending application, a driving shaft provides an effective stroke in which pins of a CPU and contacting terminals in a base member may be effectively and electrically coupled by the movement of an upper cover member driven by the driving shaft In assembly, the driving shaft is retained on the base member via two ends thereof. However, when a force is applied on the driving shaft to rotate the driving shaft, the driving shaft is subjected to a force parallel to the axial direction of the driving shaft during its entire stroke of rotation. Thus, it is likely that the driving shaft will be driven upward by such force, especially in light of the length of the driving shaft which is substantially longer for providing a long stroke for establishing desired electrical connections between the pins and the contacting terminals. Therefore, if the stroke of the upper cover member is relatively long, the connections between the pins and the contacting terminals will be adversely effected.
A main object of the present invention is to provide a ZIF electrical connector for reducing distortion of a driving shaft defined therein and further to obtain a stable stroke thereof.
In order to achieve the above object set forth, an electrical connector includes a base securely assembled to a printed circuit board, a number of terminals received in the base, a cover moveably assembled to the base and a driving device. The cover defines a number of through holes for extension of corresponding pins. The driving device is arranged between the base and the cover to move the cover between first and second positions. The base defines a lever rest which defies a central slot having a recess. The driving device includes a driving shaft and a follower. The driving shaft has a helical section and a bearing section. The bearing section bears against a central slot in a first direction and an edge of the helical section pushing the follower in an opposite second direction during an actuation stroke of the driving shaft, i.e., the period of moving the cover to the open position where the CPU pins can be freely loaded to or unloaded from the corresponding contacts. A shaft clip is located in the base and at an end of the driving shaft, and including a platform and a protrusion extended from a side of the platform. Wherein the shaft clip bears against an end of the driving shaft in the second direction and another edge of the helical section pushes the follower in the first direction during a de-actuation stroke, i.e., the period to move the cover to a closed position where the CPU pins engage the corresponding contacts.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description of the present embodiment when taken in conjunction with the accompanying drawings.